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The New Zealand flatworm (''Arthurdendyus triangulatus'') is a large land flatworm native to New Zealand. It can vary from 5 mm in length when hatched to approximately in mature adults. The New Zealand flatworm is considered an
invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...
in parts of Europe. This species is included since 2019 in the list of Invasive Alien Species of Union concern (the Union list). This implies that this species cannot be imported, bred, transported, commercialized, or intentionally released into the environment in the whole of the European Union.


Description

The ventral surface of the flatworm is a pale buff colour while the dorsal surface is dark brown. Young flatworms vary in colour from white to pale orange and develop their adult colouration as they grow. During the day, flatworms can be found resting on the surface of soil underneath objects in close contact with the ground. They may also be found beneath the soil surface hunting for earthworms. Reproduction involves the production of egg capsules of about 8 mm in length. The capsules are shiny, flexible and cherry red in colour at first and later darken to black after several days. After an unknown incubation period, several pale, tiny flatworms hatch out of the brittle capsule. One egg capsule is produced at a time with the bulge clearly visible in the dorsum of the adult worm.


Locomotion

When at rest, ''A. triangulatus'' rolls itself up and can appear like a very tiny Swiss roll. When it starts to move, it uncurls, at the same time as the circular muscles beneath the epidermal cells at the anterior end contract. The paler head-end extends forward, becoming as thin as the lead in a pencil. During movement it is repeatedly raised a couple of millimetres from the substratum before being lowered again. As movement continues, circular, diagonal and longitudinal muscles in the rest of the body contract. Friction between the ventral surface and the substratum is reduced by mucus produced by the ciliated epidermal cells. ''A. triangulatus'' can achieve speeds of up to 17 m per hour.


Invasive species

The New Zealand flatworm is an
invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...
in Europe, feeding there almost exclusively on
earthworms An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. Th ...
. This degrades
soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
quality. European earthworm predators are reluctant to eat it although cases of frogs and beetle larvae consuming flatworms have been recorded. It has been seen in
England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
,
Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...
,
Northern Ireland Northern Ireland ( ga, Tuaisceart Éireann ; sco, label= Ulster-Scots, Norlin Airlann) is a part of the United Kingdom, situated in the north-east of the island of Ireland, that is variously described as a country, province or region. Nort ...
, The Republic of Ireland and the
Faroe Islands The Faroe Islands ( ), or simply the Faroes ( fo, Føroyar ; da, Færøerne ), are a North Atlantic island group and an autonomous territory of the Kingdom of Denmark. They are located north-northwest of Scotland, and about halfway bet ...
. It might have arrived in the early 1960s, being first recorded in
Belfast Belfast ( , ; from ga, Béal Feirste , meaning 'mouth of the sand-bank ford') is the capital and largest city of Northern Ireland, standing on the banks of the River Lagan on the east coast. It is the 12th-largest city in the United Kingdo ...
in 1963. The New Zealand flatworm is easily transported accidentally in plant pots in adult or egg form. They tend to be common in garden centres and may have arrived in the UK with exotic plants. It has been suggested that they might thrive in parts of western Norway, southern Sweden, Denmark, Germany and northern parts of Poland, if they invade these regions. Similar invasions of other terrestrial
planarian A planarian is one of the many flatworms of the traditional class Turbellaria. It usually describes free-living flatworms of the order Tricladida (triclads), although this common name is also used for a wide number of free-living platyhelmint ...
s are occurring in many other parts of the world. For example, planarians of the genus ''
Bipalium ''Bipalium'' is a genus of large predatory land planarians. They are often loosely called "hammerhead worms" or "broadhead planarians" because of the distinctive shape of their head region. Land planarians are unique in that they possess a "creep ...
'' are widely distributed in North America, and planarians of the genus '' Platydemus'' on many islands in the Pacific.Sugiura, S. 2010. Prey preference and gregarious attacks by the invasive flatworm Platydemus manokwari. Biological Invasions 12:1499-1507. ''
Platydemus manokwari ''Platydemus manokwari'', also known as the New Guinea flatworm, is a species of large predatory land flatworm. Native to New Guinea, it has been accidentally introduced to the soil of many countries, including the United States. It was als ...
'' has recently (2013) been found in Europe.


See also

*
Invasive species of New Zealand origin Some species endemism, endemic to New Zealand are causing problems in other countries, similar to the way introduced species in New Zealand cause problems for agriculture and Biodiversity of New Zealand, indigenous biodiversity. Animals *The New Z ...


References


External links


Information about the flatworm
at the Central Science Laboratory (CSL), United Kingdom
Factsheet
at the European Network on Invasive Alien Species {{Taxonbar, from=Q2698648 Geoplanidae Worms of New Zealand Taxa named by Arthur Dendy